D is for Duplication; D is for Duplication

From here: “The stencil duplicator or mimeograph machine (often abbreviated to mimeo) is a low-cost printing press that works by forcing ink through a stencil onto paper. Mimeographs…were a common technology in printing small quantities, as in office work, classroom materials, and church bulletins. Early fanzines were printed in this technology, because it was widespread and cheap. In the late 1960s, mimeographs… were gradually displaced by photocopying and offset printing.”

This is just one of many technologies